Zebra Stripes Evolved to Keep Biting Flies at Bay

Why zebras evolved their characteristic black-and-white stripes has been the subject of decades of debate among scientists. Now researchers from Hungary and Sweden claim to have solved the mystery.

The stripes, they say, came about to keep away blood-sucking flies. They report in the Journal of Experimental Biology that this pattern of narrow stripes makes zebras "unattractive" to the flies.

They key to this effect is in how the striped patterns reflect light. "We started off studying horses with black, brown or white coats," explained Susanne Akesson from Lund University, a member of the international research team that carried out the study. "We found that in the black and brown horses, we get horizontally polarised light." This effect made the dark-coloured horses very attractive to flies.

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